The present invention relates to a ribbon guide device which is provided in a printing machine, such as a typewriter, word processing equipment, or the output machine of a computer.
In general, in printing machines of this type, printing paper on an elongate platen extending along a printing line is printed by the use of, for example, a fabric or carbon ribbon for a dot printer or a thermal transfer ribbon which is interposed between the platen and a printing head facing the platen and reciprocating through a predetermined traveling stroke along the printing line. The ribbon is contained in a ribbon cassette (generally referred to also as a ribbon cartridge) which constitutes ribbon supply means, and is partially exposed from the cassette through a pair of ribbon apertures. The exposed portion of the ribbon is stretched throughout the traveling stroke of the printing head, constituting an effective printing ribbon portion.
The exposed ribbon portion is movably supported by and stretched between a pair of ribbon guide members which constitute ribbon guide arm means disposed individually corresponding to the two ribbon apertures.
The traveling stroke of the printing head, i.e., the maximum printing width, is defined in accordance with the maximum width of the recording paper used. If the effective printing ribbon portion is to cover the whole traveling stroke, the ribbon cassette or ribbon supply means itself need be long enough to extend throughout the traveling stroke. In this case, however, the ribbon guide device including the ribbon guide means will become bulky and requires a substantial space inside the printing machine, complicating the layout of other components such as a drive mechanism including a motor. Thus, it is difficult to reduce the general size of the printing machine. Moreover, the ribbon cassette requires a wider storage space when unloaded from the printing machine.
As a means for settling the above problem, ribbon guide devices are conventionally known in which one of two guide arm members is slidable or rockable relatively to the body portion of a cassette so that a longer effective printing ribbon portion is secured by sliding or rocking the guide arm member. One such prior art ribbon guide device is disclosed in, for example, Japanese Utility Model Disclosure No. 57-101046.
However, in the disclosed ribbon guide device, whether of a slide type or of a rocking type, the extension length of the ribbon guide arm member cannot be made very great. A greater extension length would highly complicate the construction of associated members. Therefore, the ribbon guide device of this type cannot easily be applied to printing machines with a great maximum printing width.
In the device described above, moreover, it is necessary to secure the traveling stroke of the sliding or rocking ribbon guide arm member as a required space inside the printing machine, so that other components must be arranged without interfering with such space. Thus, problems still remain unsettled as regards the difficulty of the layout of the individual members and of miniaturization.